1. Field of the Invention
The present invention relates to a mounting apparatus to mount a surface-mounted device (hereinafter referred to as SMD) onto a SMD receiving device, in which the SMD and the SMD receiving device are contacted and then ultrasonic vibration is applied thereto to bond the SMD and the SMD receiving device each other.
2. Related Background Art
Conventionally, ultrasonic bonding has been used as a method of mounting a SMD, which is an electronic device such as a flip chip, on a SMD receiving device such as a circuit board. The ultrasonic bonding applies ultrasonic vibration while a SMD is pressed onto a SMD receiving device by a bonding tool, and causes a friction between junction surfaces of the SMD and SMD receiving device to bond both devices.
A conventional mounting apparatus using ultrasonic vibration will be described with referring to drawings. FIGS. 5A and 5B are diagrams showing steps of mounting using a conventional mounting apparatus. A conventional mounting apparatus 801 includes a holding unit 808 for holding an electronic device 809, an infrared irradiation lamp 818 for heating the electronic device 809 which is arranged below the holding unit 808 and is held by the holding unit 808, a bonding stage 803 on which a circuit board 804 on a top face of which an electrode 804a is provided is placed, and a vibrator 811 which is connected to the holding unit 808 and applies vibration to the electronic device 809.
In the mounting apparatus 801 with the above-mentioned construction, the holding unit 808 holds the electronic device 809 by using a suction, and the infrared irradiation lamp 818 heats the gold electrode 809a of the electronic device 809 from underneath (FIG. 5A).
Next, the mounting apparatus 801 brings the holding unit 808 holding the heated electronic device 809 close to the bonding stage 803, and while the gold electrode 809a of the electronic device 809 and the electrode 804a of the circuit board 804 are contacted and pressed with each other, applies ultrasonic vibration from the vibrator 811 between the gold electrode 809a and electrode 804a to bond and complete mounting of them (FIG. 5B) (refer to Japanese Patent Application Laid-Open No. 2003-197683).
In addition, as another example of the conventional mounting apparatus, there is a bonding apparatus which connects an electronic device with a circuit board using a bonding material, such as a solder bump. This mounting apparatus includes a laser equipment and has construction of bonding an electronic device and a circuit board by irradiating holding unit with a laser beam without irradiating the electronic device directly with a laser beam, and melting the bonding material through the holding unit and electronic device (refer to Japanese Patent No. 3368494).
When a SMD is mounted on a SMD receiving device by ultrasonic bonding as mentioned above, it is preferable to heat the SMD in order to strengthen the bonding strength.
As a result of wholehearted research, the present inventors have found that, in a mounting apparatus which is equipped with a heating unit in SMD holding unit, an oscillation characteristic of the SMD holding unit changes due to the difference between the materials of the heating unit and SMD holding unit, and hence, it is difficult to apply predetermined ultrasonic vibration between the SMD and the SMD receiving device. Therefore, the mounting apparatus equipped with the SMD holding unit which is not affected by the change in the oscillation characteristic is required.
Japanese Patent Application Laid-Open No. 2003-197683 relates to a mounting apparatus in which the infrared irradiation lamp 818 and the vibrator 811 are spaced apart from each other, and is not affected by the change in the oscillation characteristic of the holding unit 808. By the way, this mounting apparatus heats the electronic device 809, thereafter moves the holding unit 808 to the bonding stage 803, and bonds the electronic device 809 and circuit board 804. However, in this construction, it is difficult to perform the bonding at temperature suitable for ultrasonic bonding since the temperature of the heated electronic device 809 drops while it is moved, so that the electronic device and the circuit board may not reliably be bonded.
If the electronic device 809 is miniaturized further from now on and dimensions of the holding unit 808 is downsized, the heat radiation from the holding unit 808 will be enhanced, and it would be expected that it becomes much more difficult to maintain the electronic device at the predetermined temperature.
In addition, it is conceivable to provide the laser equipment disclosed in Japanese Patent No. 3368494 in an ultrasonic bonding apparatus like that disclosed in Japanese Patent Application Laid-Open No. 2003-197683 to adopt such construction of radiating holding unit with a laser beam and heating it. However, when the laser beam is used, although it is possible to heat a specific position of the holding unit, it is difficult to heat a certain region uniformly. Furthermore, when the laser equipment is mounted on the holding unit, an oscillation characteristic of the holding unit which transmits ultrasonic vibration to an electronic device may change, and hence, it becomes difficult to give the predetermined ultrasonic vibration between the electronic device and a circuit board.
Moreover, when the laser equipment is adopted, construction of a mounting apparatus becomes complicated or it is difficult to irradiate with the laser beam the holding unit which moves so as to transfer the electronic device. In consequence, it is difficult to maintain the electronic device in temperature suitable for ultrasonic bonding, so that the electronic device and the circuit board may not reliably be bonded.